1. Field of the Invention
The present invention relates to a paper binding device that performs a binding operation with respect to paper sheets; a paper processing apparatus that includes the paper binding device; an image forming apparatus that includes the paper binding device; and an image forming system that includes the paper binding device.
2. Description of the Related Art
A conventional image forming system is known in which a paper processing apparatus includes a paper binding device that performs a binding operation with respect to a bundle of paper sheets on which images have been formed by an image forming apparatus.
In Japanese Patent Application Laid-open no. 2010-184769, a pressure-bonding-type paper binding device is disclosed that implements a pressure-bonding binding method in which strong engagement of a bundle of paper sheets is achieved without the use of metallic needles but with the use of pressure-bonding teeth portions that are pressure-bonding members forming a pair of uneven teeth portions. As a result, the paper fiber of the paper sheets gets tangled, and the bundle of paper sheets gets bound by means of pressure-bonding of the paper sheets.
In this paper binding device, one of the pair of pressure-bonding teeth portions is a fixed pressure-bonding teeth portion assembled to a fixed member, and the other is a movable pressure-bonding teeth portion that is assembled on a movable member which is detachably attachable to the pressure-bonding member assembled to the fixed member.
As a result of binding a bundle of paper sheets by means of pressure-bonding binding instead of using metallic needles, the time and effort required for removing metallic needles from the bundle of paper sheets can be saved at the time of discarding or strip-shredding the bundle of paper sheets.
However, when a bundle of paper sheets is to be strongly engaged using the pair of pressure-bonding teeth portions, it is necessary to apply a strong pressure force. Hence, while releasing the engagement of the pair of pressure-bonding teeth with respect to the bundle of paper sheets, there are times when the bundle of paper sheets that has been subjected to pressure-bonding binding sticks to the movable pressure-bonding teeth portion and moves in the direction in which the movable pressure-bonding teeth portion moves away from the fixed pressure-bonding teeth portion. In case a bundle of paper sheets sticks to the movable pressure-bonding teeth portion, it may cause paper jam and damage to the paper sheets.
In view of the issues mentioned above, there is a need to provide a paper binding device in which a bundle of paper sheets that has been subjected to paper-binding bonding can be prevented from sticking to the movable paper-bonding member; to provide a paper processing apparatus that includes the paper binding device; to provide an image forming apparatus that includes the paper binding device; and to provide an image forming system that includes the paper binding device.